Arched girder



2 Sheets-Sheen I.

(No Model P.H.JAGK SON. ARGHBD GIRDER;

Patented 0st. 3, 1882..

2 Sheets-Sheet 2.-

(No Model.)

-P. H. JACKSON.

ARGHED GIRDBR.

Patentedflot. 3 1882.

UNTTED STATES PATENT FFICE.

PETER II. JACKSON, OF SAN FRANCISCO, CALIFORNIA.

ARCHED GIRDER.

SPECIFICATION forming part of Letters Patent No. 265,321, dated October3, 1882.

Application filed April 11,1882. (No model.)

To all whom it may concern Be it known that I, PETER. H. JACKSON, of thecity and county of San Francisco, State of California, have invented anImprovement in Arched Girders; and I hereby declare the following to bea full, clear, and exact description thereof.

My invention relates to certain improvements in the construction ofsectional cast-iron arched girders by which the tensile strain upon thetie-rods and the compressive force upon the cast-iron arch are betterdistributed and equalized.

It consists in such a construction that the abutting parts of thesectional arch always meet on a line with the intrados of the arch,whatever may be the deflection under loads, and also in connecting thejoints or meeting ends of the sections with the tie-rods byinterveilingvertical connecting-struts, which serve to transmit the strain from archto tie-rods, so that any deflection of the arch is resisted by theti'c-rods, and all vertical strains are resisted by both the arch andthe rods.

Referring to the accompanying drawings for a more complete explanationof my invention, Figure l is a side elevation of an arch of myconstruction. Fig. 2 is an enlarged portion of the same. Fig.3isaview ofthe meeting ends. Fig. 4 is a transverse section. Figs. 5 and 6 aremodifications of the same.

My present invention is an improvement upon one which was patented to meNovember 28, 1871. This previous patent contemplated such a constructionof the sections of an arch that the pressure should be distributeduniformly over the abutting surfaces under any load; but I have foundthat when subjected to great strain the tie-rods become extended, sothat the arch sinks proportionately, and instead of the pressure beingdistributed evenly over the whole of the meeting ends it was transferredentirely to the top or extrados of the .arch, which thus sustained allthe compressive force due to the tensile strain upon the tie-rods. If,on the contrary, the arch is made in a single casting, the wrought-irontierods will, when subjected to strains, become elongated, a certainsmall proportion of their length depending upon the load, and this willallow the arch to become depressed, so that a considerable tensilestrain willbethrown upon the intrados of the arch, which east-iron iscomparatively feeble to resist.

In my present invention, A A are the sections of the cast-iron arch.These sections,ot' which there may be any suitable or desired number,are made of sufficient width and depth, and have flanges B and O at thetop and bottom. Upon one of'the meeting ends is formed asemi-cylindricalprojection, D, which extends across the full width of the abutting face,as shown. The opposite abutting face has a corresponding recess orsocket, E, into which the projection D fits, resting against the bottomof the depression, and as the arc of the depression is shorter than thatof the cylinder it will be seen that the opposite faces or ends of thesections above thisjoint will not come together under any deflection,and thus allow of considerable movement about the joint. This joint isformed so that its center is in the line of the lower rib, O, orintrados of the arch, and thus the whole compressive force is exerted inthis line. As the upper portion of the sections do not come together, itwill be seen that the arch may be subjected to considerable deflectionswithout changing the line of compression, which will always be throughthe center of the joint and in the line of the intrados. In some casesthis joint is formed by making a concavity or depression in each of theabutting ends in a line with the intrados of the arch, and forming acylindrical head upon the top of the strut G, which is inclosed by theseconcavities, as shown in Figs. 5 and 6. This cylindrical head is madeshorter than the full width of the arch-sections, and the sections A arecast with projections to, which extend across the concavities, thusforming a closed end, which retains the head D in its place. Tlle loweredges of the meeting ends of the sections in both cases will meet andprevent the rising of the jointfrom a load at some other point of thearch.

The tie-rods F, formed of wrought-iron, extend from one end to the otherof the arch, forming a chord to it. They may be' as many in number asare found necessary, lying side by side and parallel with each other.

From each joint or point of meeting of the sections A a strut, G,extends vertically downward, and has grooves or arches made in the lowerside to fit upon the tie-rods, so that when the load is brought upon anyportion of the arch, so as to deflect it, itis partially transferred tothe rods, and, by increasing their tension, resist further compression.

By this mode of construction the tensile strain at the intrados of eachof the east sections, due to the load upon that section, may beneutralized by the compressive resistance in that particular sectioncaused by the tensile strainupon the tie rod in the Whole system.

Having thus described my invention, What I claim as new, and desire tosecure by Letters Patent, is-- 1. In an arch composed of castironsections A, thejoints formed of the transverse cylindrical projections Dupon one section, and the corresponding depression, E, in the face ofthe opposing section, said joints being in a line with the intrados ofthe arch, substantially as and for the purpose herein described.

2. In an arch or girder, and in combination with the sections A, havingthe joints- D E, formed in a line with the intrados of the arch, thetie-rods F, extending from end to end of the arch and forming chordsthereto, substantially as herein described.

3. In an arch or girder consisting of the sections A, with their jointsD E, formed in line with the intrados of the arch, and the tie rodsPETER II. JACKSON.

Witnesses:

G. W. EMEnsoN, S. II. Nonnsn.

